Method of and apparatus for separating liquids and solids



Jury 9, 1929. w, EDDISQN 1.720.211

METHOD OF AND APPARATUS FOR SEPARATING LIQUIDS AND souns Filed March 14, 1925 3 Sheets-Sheet 1 'WMM ATTORNEY July 9, 1929. w. B. EDDISON METHOD OF AND APPARATUS FOR SEPARATING LIQUIDS AND SOLIDS Filed March .14, 1925 3 Sheets-Sheet BY C g MATroRNEY Betcha d July 9,1929; v v i 1,720,211 UNITED STATES PATENT OFFICE.

WILLIAM: BARTON EDDYISON, or mvmo'roiv, NEW YORK.-

mn'rnon on Man APPA ATUS For. SEPARATDIG LIQUIDS AND SOLI'DS'.

Application fi-led March 14, 1925. Serial No. 15,443.

' This invention relates to a method of and this accordin to the character of the solid apparatus for separating liquids and solids. material an the filtering pressure em- In separating the liquid and solid constituployed. I have found that a further sepaents of a mixture of liquid and suspended ration of liquid from the fil er cake may be 5 solid matter by means of a filter press, a secured advantageously by! subjecting the considerable portion of the liquid remains cake to pressure, most desirably between the as excess water in the filter cake. Thls filtering surface and a pressing. member. In? makes it necessary, when the object is to this way substantially all of the excess liqrecover the liquid or a substancein solution uid may be very quickly squeezed out of 10 in the liquid, to wash the filter cake, usually the cake. When the object is to recover the by. passing water or other suitable liquid llquid, the application of a sufiicient squeezthrough the filter press while the cake relng pressure for a sufficient but relatively 1 mains on the filtering surface. This results short time will result-in the separation from v in dilution of the separated liquid and. inthe solid matter of all its .contained liquid 15 creases the .cost of concentrating the liquid excepting the poreliquid and a very small and of recovering substances in solution in percentage, which may be aslow as'a fracthe liquid. -When the object is to recover tlon of 1%, of excess liquid. Andpressurev the solidmatter, it is in most cases necessary so applied to the moist filter cake apparently to subject the filter cake to a. drying opera causes some re-arrangementof the particles 20 tion for the purpose of removing a further of solid matter by which re-arrangement the amount of the liquid. The present invention pores or spaces between the particles are aims to 'get at a minimum 0081311116. in a somewhat reduced so that the pore liquid minimum amount of time, the maximum retained by the cake of solid matteris less possibleseparation of the constituents of'a than the amount \of pore liquid which "th 25 mixtureof liquid and solid matter, whether cake would otherwise have. After subjectthe purpose be to recover the liquid or to mg a filter cake of common insulator clay recover the solid matter; to recover the liqone IIlCll thick to a squeezing pressure of 450 uid witha minimum of dilution, and to lbs. per square inchfora period ofv fifteen produce a filter cake of desired predeterminutes, I-have'found the clay to contain -mined liquid content and uniformly moist less than .7% of excess water, the amount of throughout. pore water being about.14 .2%. y The invention comprises'a method where- When the "object is to recover the solid .in the greater .portion of the liquid is sepamatter, the application of the squeezing pres-v rated from thesolid matter: of the mixture sure to the fil lflf -ke akes it possible not 1 by filtering, and the filter cake is then subonly to'reduce the liquid content of the cake jected to'squeezing pressure whereby a furto a fraction of 1% of liquid in excess of ther amount ofliquid is expressed there the pore liquid, but, also, the liquid content from." The invention also comprisesfan ap-- may be quickly and accurately; reduced to fparatus for carrying out the'method. any desired predetermined amount between As -stated, in separating the liquid and that of the filter cake as left after thefiltersolid constituents of a mixture of liquid and ing step and the pore liquid content oflthe suspended solid matter in a filter press, a material. -The amount to which the liquid ,considerable amount of liquid remains in contentof any given material is reduced will the filter cake, and this is so even when the dependupon'the degree of pressure applied, 45 liquid mixture is forced against the filtering for sufiicient time, to the filter cake; that is, surface under avery considerable pressure. the degree of pressuremaintained for a suf The total liquid content of. the filter cake ficient length of time will determine the' will be in the neighborhood of 25% by liqpid content of the squeezed-material or weightwhen the solid matter is a'clay 'mix'-' ca e, and the length of time forwhich the ture such as is commonly used for. making pressure must be maintained will depend on electrical insulators and the liquid mixture, the character of the material andv on the or slip, has been forced against the filtering thickness of the cake. 1 I have found for a surface under about a'hundred pounds prescake of one inch thickness the time required sure, about one-half of this 25% being pore ,to .express substantially all -the' possible water and one-half being excess water. The liquid at a given pressure to vary from four' liquid content may be more or less than minutes to two hours according to the chari i-"providing an ceramic products by content of 3 any constructed with a series ,of'

aeter of the material. An open clay such, as isused in making saggers has taken the min imum length of time, and a fine retort clay such as is used in the manufacture of zinc retorts has taken the maximum length of time. Maintaining the pressure on the cake ,beyond the "required minimum period does not result in any further reduction of the liquid content; and the degree of moisture of the cake at the time the pressure is applied, While it affects slightly the time for which the pressure must be'maintained, has no other effect upon the final moisture content of the pressed cake. Increase or decrease in the degree of pressure applied will" result in a corresponding decrease or increase of the liquid content of the treated material. When the degree of pressure has once been determined for reducing the liquid given material to a desired amount, this predeterminedliquid content of such material may thereafter be produced by applying such determined pressure for a sufiicient time; and the required time for maintaining such pressure in a given sized mass or cake of such material may also readily be determined.

The apparatus. forming part of the present invention .and which is most desirably used for practicing the method comprises afilter press having pressing means whereby the filter cakes are pressed between the filtermg surface and such pressing means. The press is most desirably of the plate type, partition and drainage plates which alternate with and are separated by spacing frames carrying each a flexible inflatable member which during the time that the filter cakes are being built up on the filtering surfaces ,carried by the drainage plates are deflatedand stand off awa from the filtering surfaces, and which after thefilter cakes are formed are inflated and their walls forced by fluid pressure against the" filter cakes to compress the cakes against the drainage plates. The invention on its apparatus side includes various @features of construction and arrangement of taken on line 5-5 of Fig. '2;

parts as hereinafter set forth.

The invention is capable of wide application in the separation of variousliquids and solids and for conditioning various solid -materials. "It is considered of special value improved method and apparatus for .conditioning clay and other *plastic earthyfmaterials for the molding of what is known as the dry-press process, in which the material is pressedinto the desired shape in a die. In producing molded articles in this way, the pulverized, i. e., finely should have the right moisture content and should be uniformly moist throughout. The

press molding, in which the filter cakes present method of conditioning clay for drytained by filter-pressing, the mixture of clay and a large excess of water are removed from-the filter press 'to a steam-heated dryer Where they remain for a period of from several hours to overnight and are'then put through a tempering process to secure the desired right and .uniform -moisture I content, involves very considerable time and labor expense and is otherwise unsatisfactory, being inexact and leading to much difficulty in having clay of the right moisture content ready for pressing, especially after week-ends and holidays. The present invention reduces greatly the time required for conditioning clay for dry press work and makes it possible to produce more surely and reliably and at much less cost a better conditioned clay having the desired moisture coptent and uniformly moist.

A full understanding of the invention can best be given by complete apparatus embodying the apparatus features of the invention and adapted a detailed description of a for use in carrying out the method, and of drawings illustrating such an apparatus of a portion of the press and dryer on an enlarged scale and showing parts separated for the removal of the filter cakes from one of'the drainage plates; I i

Fig. 3 is a transverse sectional view showing one of the drainage plates with filter cloth thereon partly broken away, and showing also a par-t of one of thespacing rings.

with a portion of the pressure bag carried thereby; p

' Fig. 4 is a transverse sectional'view showingone of the spacing rings in elevation with the pressure bag carried-thereby, Figs. 3 and 4 being on a scale between those of Figs. 1 and 2;

Fig. 5 is an enlarged detail sectional view Fig. 6 is a detail view ,of parts shown in Fig. 5. but -separated from each other; and

Fig. 7 is an enlarged view of a portion of the face of one of the spacing rings and a part of the pressure bag carried thereby.

Referringto the drawings, the apparatus shown comprises a series of alternating drainage plates 10 and spacing frames or rings 11 which are hung on the upper two of four tension members or bars 12 which extend between press ends 13 and 14. The

divided, materialppress end 1%. is formed with a hydraulic cy1-.

inder 15, partly shown, in which moves a piston 16 which carries at its'inner end a I pressure plate 17. The piston 16 and its pressure piate 17 act to press and hold the gauze, or fine wire netting,

draina e plates and spacing frames together when t 1e hydraulic pressure is on the piston. Withdrawal of the piston l6 permlts the drainage plates and spacing frames .to be separated for removal of filter cakes formed on the filtering surfaces of the drainage plates. The press may be made with any desired number of filter pressing units, each consisting of a spacing frame and the adjoining drainage plates, and the plates and frames may be of any suitable size, according to the desired capacity of the press. a

The spacing frames or rings 1A are most desirably of annular form and are hung on the urmer tension members 12 by means of brackets 20, so that the rings may be moved longitudinally of the tension members when not held, pressed between adjoining drain age plates. The drainage plates 10 are solid plates of metal or other suitable material of a size to correspond to the spacing rings, and desirably, having surfaces sufficiently large to extend somewhat beyond the outer circumference of the rings. They, a'reconvenlently made ,of octagonal shape as shown to fit within the four tension members and are hung on the two upper tension members by projections, or brackets, 21. The two faces of each plate are covered by afilter cloth 22, except that the end plates need have the filter clot-h only on their inner faces. The filter cloths for covering the two faces of a plate are conveniently formed in a single piece hung over the top ofthe plate as shown,

' and means such as the holding strips 23 are desirably provided for holding the shaped filter cloths in place when the plate is separated from the adjoining spacing rings. The faces of the plates are formed to permit draining off of liquid which passes throughthe filter cloth, and for this purpose the plates are provided with coverings of wire 24.. This wire gauze is of sufiicient strength and of sufficiently fine mesh to support the filter cloth and at the same time provide the necessary flow-ways for the draining off of the. liquid The filter cloth may be any suitable cloth impervious to the solid matter of the mixture or other sheet material mit'the passage of the filtrate while holding back the solid matter. For a purpose hereinafter explained, an outer portion 25 of each filter cloth is made impervious to the passage of the filtrate, as by being provided with a coating of rubber composition or other suitable impervious coating, and this impervlous portion or coating extends inward a short distance beyond the line of contact with the filter cloth of the inner edge of the spacing ring, leaving a 4 central uncoated pervious filtering portion of .the filter cloth of a diameter somewhat less than the inner diameter of the spacing rings.

Each of the spacing rings 11 carries 9.

suitable to per-' be tightly clamped together .in nipple, threaded end with a shoulder 35 and the thread is cut away for a distance from the flexible inflatable pressure member- 30 which is formed by a bag having walls offlexible rubber or other suitable elastic flexible and expansible material. The bags are made to have flat parallel sides when deflated and I are round and of a Size to fit with a circumferential groove in which the edge portion of the bag seats when forced outward by its holding ring 31. The bags are formed with radially extending filling tubes or necks 32 of the same material as the bag, and each spacing ring has a radial opening in which through which the neck of the-bag extends and which has a threaded outer end for connecting a branch from a pressure fluid manifold. The ends of the rods 31 are cut away,

as shown in Figs. 5 and 6, to form flat-faced overlapping portions having registering threaded holes to receive the threaded end of a short tube or nipple 34 which serves to secure the ends of the rod 31 together and the outer end of which extends into the filling tube or neck 32 of the bag.

rWhen a bag is to be positioned in its spacin ring, it is placed in position with the en s of its holding ring 31 disconnected within the rings is screwed a bushing 33 and the ring contracted. The ends of the 4 ring rod are then manipulated through the flexible walls of the bag and forced apart to expand the ring-and to bring the rod ends to their normal overlapping position withtheir threaded holes'registering with each other." The nipple 34, positioned in the hole of the outer overlapping rod end, is, then screwed into extend into the threaded hole of the inner overlapping rod endand to fasten the overlapping ends'secu'rely togeth er. In order that the overla ping ends may 'y the screwedthe nipple is fornfed beyond its shoulder equal to or slightly greater than the thickness of the outer end, so that when the, shoulder 35 comes into overlapping rod engagement with the outer rod end, the v nipple thread will be actingonly on the 'inner'ovei'lapping rod end and further turning of the nipple will, therefore, cause the rod ends to be tightly clamped together.

,The' bags are desirably of such size that normally, i. e., when deflated, they will be held under slight tension by the holding rings 31, this slight tension serving to hold is desirably sloped "her tube against the wall of A tight joint is thus provided between the v of the bagwalls ing since the high and . under any suction appliedwto tlie sides of the deflated bags flat and preventing the deflated bag from buckling and interfering with the formation of the filter cakes. Instead of depending on the tensionto hold the wallsflat when the bag is deflated, a positioning sheet or thin plate 36 .may be provided ineach bag This plate may be of corrugated metal or of wire netting or of other suitable material and form. Such a plate is shown in one of the bags shown in Fig. 2. Such positioning plates will hold the walls of the collapsed bags flat even though the walls. are not under tension, but most desirably the bags will be under slight tension when deflated even when the positioning plates are provided; The inner face of each spacing ring inward from the bag seating groove as shown at 37 and 38 to provide slanting seats for the outer or edge portions of the bag sides inorder to avoid the straining of such edge portions of the bag which might otherwise result when the bag is inflated.

The filling tube or neck 32 of each bag is secured in the bushing 33 by means of a short tube 40 which is inserted in the outer portion of the tube 32 and has its outer end tapered or outwardly flared to force the rubthe bushing.

of the bag and the bushpressure used in expandthe bag tends to make the joint tighter, friction holds the tube 40 in place under the negative pressure used in exhausting the bag. The tube 40 extends inward to the nipple 34 in order to provide a free passage and prevent collapse of the rubber tube deflating the bag; The meeting ends of the tube 40 and of .the nipple 34 are desirably cut away, one externally and theother internally, to provide a telescoping joint and give substantially continuous support for the rubber tube. 'Each bag is connected to a pressure fluid manifold .41 by meansof a flexible tube 42 which is connected tothe end of the bushing '33 by a connection'43.

Each spacing ring has an inlet opening 45 for supplying the mixture of liquid and iolid matter to be filtered to the filter chamer, jacent drainage filling tube or neck plates when t e press membersare assembled and clamped in filtering position. The mixture to be filtered, usually termed slip? when the mixture is one of clay and water, is supplied to the inlet openings 45 of the spacing rings from a supply manifold 46 through flexible tubes 47 which connect screwed into the epenings 45. The flexible connections between the. manifolds 41 and 46 and the spacing rings permit the spacing or space within the ring between ad to' tubular connections '48.

rings to be moved back and forth for unloading. and resetting the press. rubber hose may be used for the connections 47 from the supply manifold 46, but. the.connections 42 from the pressure manifold 41 are, because of the higher pressures employed, desirably made of suitable flexible The slip inlet openings 45 are branched to supply. the slip at each side of the bag, and the branches extend outward to th side faces of the ring, each branch opening into a short circumferentially extending groove 50 from which several shallowgrooves 51 lead inward to the'inner edge of the face of the ring; The supply passages thus provided opening into the filter chambers, while small as they-desirably should be, As the side faces of the ring rest against the impervious portions 25 of the filtercloths on the drainage plates when the plates and rings are assembled together, the grooves-5O and 51 provideclosed passages leading from the inlet openings 45 tothe filter chambers. In order to prevent the walls of th'e bags from being forced into the openings at-the inner ends of the grooves 51 when the bag pressure is on, the bags. are provided with patches 52 of stretchable but'flexib'le material over the portions which come opposite the ends of the grooves- 51 when the bag is'inflated.

- In the use of the. apparatus, plates a d spacing rings "eing moved into closed plsition and held pressed together by the hy aulic piston 16, and t e drainage plates having as shown, and the, pres lapsed so that their si away from the filtering surfaces,- the slip. or 'other mixture of liquid and suspended solid matter tobe filtered isturned on to flow from the supply manifold 46 through the flexible pipes 47 and inlet openings 45 into the filter chambers? The slip fills thefilter chambers and, being supplied under suitable pressure, is forced against the filtering surfaces provided bythe filter cloths on the drainage" plates, and filtering takes place in --theiusual manner, the filtrate draining o over the surfaces of the drainage plates, and the filter cakes building up on the filtering surfaces. The filtering operation will be continued until the filter-cakes have been built up to the desired thickness, the time required for forming a cake of a given thickness depending upon the character of the solid material in the mixture and upon the pressure under which the mixture is forced into the press. The resulting filter cakes will contain a considerable amount of liquid inexcess of the pore liquid, the exact liquid content depending on the character of the material and the filtering pressure.

When the filter 'cakeshave been built up Suitable.

are readily accessible for cleaning.

the drainage been fitted with filter cloths ure bags being coles are withdrawn.

, pressing position to the desired thickness,"

the feeding of the mixture to the press is stopped, and the pressure fluid; is then admitted to the pres-.

time. \Because of the hlgh pressures used liquid content 'of the cakes has been reduced to an amountdependent upon the degree of pressure applied to the cakes. After the pressure has been maintained for the necessary time it is cut off and a negative pres sure is applied to the manifold 41 to draw the water from the bags and collapse the bags, the sides of the bags drawing away from the pressed filter cakes'and returning to their-normal position. Fig. 2 shows. at

the extreme left a pressure bag expanded to by the fluid admitted %1IOllghdt5 neckand fastening nipple 34. he bag inthe next. frame to the right in this figure is shown as it appears when collapsed back to its normal position. For removing the pressed filter cakes from the filter press, the hydraulic piston 16 is withdrawnand the drainage plates and spacing rings are successively moved to the right to space successive drainage plates away from the adjacent spacing rings sufliciently for removal of the filter cakes therefrom. When the rings are-thus separated from a plate, as shown at the right in Fig. 2, the'filter cakes will hang on the filter cloths from which they may. be readily separated to drop down from the press.

Because of the impervious'outer portion 25 of the filter cloths which extend a short 7 distanceinward from the inner edge of each spacing ring and prevent the passage of the filtrate through these outer portions of the filter cloths, the filter cakes are prevented from extending out edgewise into contact with the spacing rings. The filter cakes will build up only from points on the filter cloth through which the filtrate can pass, and will therefore build outward from the inner edge of the impervious coating only for a distance substantially equal to the thickness of the cake, Therefore, by having the impervious coatings extend inward rom the inner faceof the spacing rings a distance somewhat greater than the thickness of the cakes to be formed, contact of the cakes with the spac ing rings is effectually prevented and the explained.

as shown in Fig. 2.

cakes, engaging only the flat surface of the cloths, are readily separated therefrom. Without this -provision of the impervious outer portions of the cloths, the cakes would build up aga nst the spacingrings and cause difiiculty in separating thee rings and the drainage plates, even though the inner faces of the rings were slanted outward instead of inward as-shown. This difiiculty would be even greater with the spacin rings formed as shown, and the ability to fiiave the rings formed with inwardly slanting inner faces high pressure for a suiiicient time they readily pull away from the surface of filter cakes and are left clean and almost dry.

When the object is to recover the liquid from the mixture of liquid and solid matter supplied to'the filter press, a very high pressure, which may be as much as 400 pounds or more to the square inch, is applied to the bags, and this pressure in a short time, usually. not more than 10 to minutes, will express substantially all the excess liquid from the filter cakes, leaving only, for

most solid materials, a fraction of 1% of pore liquid, and reducing 1 the filter cake, and thereliquid in excess of the pore space of fore, the amount of liquid which can be re-' tained by/it as; pore liquid,\as hereinbefore When the liquitl is being separated foi: the. urpose of concenti'ation and recovery there tion therein, or when for\,other reason it is 'desired to remove as completely-as possible any soluble substance from the .s id matter, the filter cakes may be washed while still remaining in position in the press by admitting to the filter'chambers, after the cakes have been pressed and the bags contracted, water or other suitalileliquid under suitable pressure ,to be forced into or thrbugh the cakes, and then admitting pressure fluid again into the bags to force back the liquid from-thel filter chambers and express again excess. liquid from the filter cakes; and this process may be repeated as desired. In this way substantially all of the substance in solution may be removed from the filter cakes with the use of an amount of water or other liquid which is relatively very small as compared to the amount required in washingt'he filter cakes in the ordinary manner.

lVhen the object is to recover the solid matter, the degree of pressure to be applied to th'efilter cakes by means of the inflated bags will depend upon and be determined by the degree to which it is desired to reduce the liquid content of the cakes. If it, is' desired to express from the cakes substantially all the liquid in excess of the pore liquid, the

rom of a substance in soluto the bags, and this pressure will be main liquid maximum possible pressure will be applied tained so long as any liquid flows from the press. By applying a lesser degree of pressure and maintaining it until after the flow of liquid from the press ceases, the liquid content of the filter cakes may be reduced to any desired amount between that of the filter cake before pressing and a content slightly above the pore liquid content. The final content'will vary according to the pressure applied, and a given pressure applied for a sufficient length of tune Wlll always result in the same liquid content of a given material. NVhen the pressure needed to secure a desired liquid content in certain material has once been to. flow from the, press.

- the press.

determined, the application of such predetermined pressure to the same material can be depended upon to give the same liquid content in the product, and this is so irrespective of the thickness of the filter cake or mass of material being pressed or of its liquid content at the .beginning of is maintained until after the liquid ceases Maintaining the pressure beyond such minimum. pressure period does not change the liquid content. Of course,-in operating with any given bag pressure, the pressure might be cut-off before all the liquid hasbeen pressed out of the filter cakes which would be pressed out under such pressure if l0nger maintained, that is, before the liquid has ceased to flow from But, if the pressure is so cut off beforethe liquid'hasceased to flow from the press, then the filter cakes will be left unevenly moist. By maintaining any given pressure on the cakes until after the liquid has ceased to flow from the press, a uniform liquid content throughout each cake is secured.

The time for which any given pressure should be maintained" to secure its maximum result and a uniform liquid content will, as stated, vary according to the character of the material being pressed, the thickness of the) material, and to a slight degree on the liquid content at the start of the pressing operation. For cakes of thesame materlal'a-nd of the same thickness, and of substantially the J same liquid content'at the start, the required minimum pressure period for' securing the maximum result of any givenpressure will always be the same, so that when suchminimum pressure period for the application of a predetermined .pressure to a filter cake of a given material and of a given thickness to reduce the liquid content of the cake to .a

predetermined uniform moisture content hasbeen once determined, then thereafter the des red result nay be obtained by the application of such predetermined pressure for such predetermined period. The period for which pressure is maintained should desirthe pressing operation, provided the. pressure .of the liquid from 'site sides of the rame,

ably be slightly longer'than the minimum required in order to provide against slight variations in the. material, the thickness of the c kc and the starting moisture content. Examples of the degree of pressure and pressure period required for securing a certain uniform moisture content in certain material have already been given. a

The WOfd fimpervious as used in the claims will be understood as meaning impervious to the filtrate-or to the pressure fluid, as the case may be, unless given a more limited meaning, as in the expression impervious to the solid matter.

What is claimed is:'

1. The method of separating liquid and solid constituents of a mixture of liquid and suspended solid matter, which comprises filter-pressing the mixture to separate liquid from of the solid matter against a filtering sure the solid matter and form a filter cake face, and separating a further amount of the liquid from the solid matter by filter cake between said filtering surface and a fiexibleimpervious surface 2. The combination with filtering means 'for separating the greater portion of the of the liquid, of means for applying pressure to the filter cake by pressure fluid acting through an impervious sheet of flexible material in contact with the filter cake to press the filter cake against the filtering surface and thereby separate a further amount the solid matter.

'3. The combination with a filter press, of means for pressing the filter cake, against the filtering surface comprising a sheet of flexible material having a smooth impervious surface for contact with the filter cake and means for supplying pressure fluid to force said sheet against the filter cake.

f1. In a filter press, the combination of a member .having a central filtering surface and an impervious surface surrounding the filtering surface, and a spacing frameadapted to be assembled with said member in engagement with the impervious surface of pressing the be separated from said member'extending' inward a short distance i from the inner edge of the spacing frame.

' 5. In a filter press, the combination of a pair of plates, a spacing frame, means for releasably holdin the plates against oppothe inwardly facing surface of each plate havingfa central filtering portion'and an outer impervious portion which extends inward a short 'dista-nce'from the inner edge of-the spacing frame, and an inflatable pressure member mounted within the frame having opposite impervious walls of flexlble material, and means for supplying pressure fluid to said inflatable member. filtered to the filter chambers within the 6. In a filter press, the combination with a drainage plate and a spacing frame and means for releasably holding the plate and frame together, of a filter cloth on the face of the drainage plate having an im ervious outer portion to prevent filter cake rom being formed, in contact with the spacing frame. p v

7. In a filter press, the combination with a drainage plate, of a filter cloth on the face of the drainage plate','and means for pre venting the flow of filtrate through an outer zone of the filter cloth within the filter chamber, the width of which outer zone,is

greater than the thickness of the filter'cake.

8. In a filter press, the combination of a drainage plate,l a filter cloth on the drainage trate through an outer zoneof the filter cloth within the filter chamber, the width of whi the filter cake against the filtering surface comprising an impervious sheet of flexible material and means for supplying pressure flulid to force said sheet against the filter ca e. 9. In a filter press, the combination of a pair of plates having on their facing sides means providing filtering surfaces, a spite-- ing frame between said plates, meansfor releasably holding the plates against opposite. sides of the spacing frame, an inflatable pressure bag mounted in the spacing frame between the lates, and means providing a filling inlet or supplying a pressure :fluid- .to the bag.

10. In a filter press, the combination of a pair of plates having on theirfacing sides means providing filtering surfaces, a spacing frame between saidplates, means for releasably holding the plates against opposite sides ofthe spacing frame, an inflatable v pressure bag'of elastic flexible and fexpansible material mounted in the spacing frame between the plates, a collapsible holding ring within the bag for holding the bag in position in the frame, and means providing a filling inlet extending through the spacingframe for supplying a pressure fluid to the 7 bag. \l 11. In a filter press, the combination of aplurality of drainage plates and a plurality 5 of spacing frames set between successive plates, means for holding the plates and frames pressed together in assembled position and for permitting the plates and frames to be spaced apart, the surfaces of 3, the plates within the frames being provided with filter cloths, means for supplying the mixture of liquid. and solid matter to be outer zone is greater than the thickness of the filter cake, and means for pressing frames jbetween ad'acent' plates, inflatable pressure members within the filter chambers,

and means for supplying pressure fluid to said inflatable pressure members. 1

12. In a filter press, the combination of a plurality ofdrainage plates and a pluralit of. interposed spacing frames between a jacent plates, releasable means'for pressing the plates and frames togetherin assembled position, filter cloths on the faces of the drainage lates, means for preventing the passa e o liquid-through an outer zone of each lter cloth within the filter chamber,"

an inflatable pressure. bag' carried by each frame having walls ofv flexible elastic and expansible material formed to be-flat when deflated and mounted with its edges held against the inner face of the frame, inlets extending through the frames for supplying pressure fluid to the pressure bags," and in'-- lets extending through the frames for supplying the mixture 0 liquid and solid matter to be filtel ed to the filter chambers at each side of the bags.

plate and a'spacing frame and means for releasably holding theplate against the frame to-form a side of a filter chamber, of

13. In a filter press, the combination of a a a covering of wire gauze on the inner face of the plate, and a filter cloth extending over the gauze, the gauze and filter cloth covering the face of the plate within the frame and extending outward between the frame and. theplate, and the filter cloth 1 lets extending through 'the spacing frames,

a mixture supply manifold, flexible supply connections between the supply manifold.

and said inlets,vinflatable pressure members having opposite 'walls of flexible material mounted in the s acing'frames, inlets extending through tiie spacing frames to said inflatable pressure members, a pressure fluid manifold, and flexible supply connections between the pressure fluid manifold and .said pressure fluid inlets.

In testimony whereof I have hereunto set my hand.

WILLIAM BARTON EDDISON: 

